Crustal structure of a young collision zone: the Arabia–Eurasia collision in northeastern Turkey investigated by magnetotelluric data

Abstract

Abstract The northeastern Turkey is located at the intensely deformed east Anatolian Collision Zone that is formed by the collision of the Arabian Plate with Eurasia. The region is one of the best examples of the continental collision zone in the world and exhibits an active north–south shortening and a young and widespread volcanism. In northeastern Anatolia, the ongoing motions of the Arabian and Eurasian Plates through a range of deformation processes have generated the Erzurum–Kars Plateau, a region of large-scale deformation and uplift observed at surface. However, the nature of deformation driven by the continental collision remains unresolved at depth. In this study, magnetotelluric (MT) data recorded at 74 sites constituting two intersecting profiles have been used to construct the characteristic electrical conductivity pattern associated with the intensely deformed east Anatolian Collision Zone beneath the Erzurum–Kars Plateau, northeastern Turkey, with the aim of imaging the 3D distribution of fluids in order to link it with subsurface rheological conditions. An equal number of colocated transient electromagnetic (TEM) sounding data were used to allow the static shift correction of the MT data; a borehole was also drilled inside the study area. We ran a one-dimensional inversion of TEM data in order to determine shift in MT data and a three-dimensional inversion using full components of MT impedance tensor previously corrected for static shift. The resulting models showed that two distinct conductive zones probably indicating local accumulation of melt exist at mid-to-lower crustal depths (15–45 km) throughout the Erzurum–Kars Plateau. The spatial distribution of these anomalously conductive zones mechanically characterizes weak areas that may permit flow of crustal materials in the collision zone. These conductive zones have been previously identified further west of the collision zone, which implies that the electrical characteristic of the collision zone is continuous from west to east beneath the Anatolian Plateau. The spatial extent of the conductive zones may suggest the presence of two localized crustal flow channels situated laterally parallel to the orogeny. These findings can potentially contribute to understanding of the crustal structure of collision zones, in particular east Anatolian Collision Zone, and the hypothesis that crustal flow can occur in orogenic belts.

Keywords

• Continent–continent collision
• Eastern Anatolia
• Erzurum–Kars Plateau
• Anatolian Plateau
• 3D inversion
• Magnetotellurics